Energy Transfer and Colorful Emission of Eu3+- and Tb3+-Co-Doped CaWO4 Phosphors

Eu³⁺/Tb³⁺-co-doped CaWO₄ phosphors were synthesized by a simple green co-precipitation process. The structure of the samples was investigated by X-ray diffraction. The photoluminescence spectra and fluorescence decay lifetimes of the samples were measured to investigate the luminescence properties. We analyzed the energy transfer process between Eu³⁺- and Tb³⁺-doped CaWO₄. As the Tb³⁺ to Eu³⁺ energy transfer process was confirmed, Eu³⁺- and Tb³⁺-co-doped CaWO₄ phosphors showed a color-tunable emission from green to red under a 365-nm UV lamp.